Trellis coding is a technique for improving the random noise immunity of a data transmission device by increasing the distance between possible signal sequences without increasing their average power. Trellis coding is widely used in voiceband data modems. Shaping is a technique that can improve random noise immunity by an additional 1.53 dB beyond what is achievable with coding.
Voiceband modems also use equalizers to combat the effects of amplitude distortion, another major impairment that can reduce reliability. Tomlinson precoding is an effective transmit equalization technique that compensates for amplitude distortion.
Recently a technique called trellis precoding was described that effectively combines coding, shaping, and precoding, providing their benefits in a joint manner. That technique allows the transmission device to operate near the theoretical limits of the transmission channel.
Transmission systems can also be impaired by transient noise phenomena such as impulse noise. Impulse noise is often due to switching equipment, but also can be caused by bit slips in digital transmission systems. When the impulses last several symbols, such noise phenomena is known as burst noise. Coded systems can resist burst noise if the effective span of the code is longer than the duration of the burst. Increasing the span of the code often requires high complexity. Thus, in practice, a device known as a deinterleaver has been utilized to reduce the duration of noise bursts. A deinterleaver can scramble the noise signal so that burst noise appears to a decoder as random. In order to preserve an order of an information signal, an interleaver in the transmitter performs an inverse operation. A combined effect of utilizing the interleaver and the deinterleaver is a pure delay.
Since interleaving destroys a certain structure of a shaping system, thus making reconstruction of a signal at a receiver impossible. With present techniques, interleaving cannot be applied to a trellis precoding system to achieve appropriate results. There is a need for a device and method for an interleaving system that randomizes bursty noise in a trellis precoding system without destroying the shaping structure.